Added ImportMaps availability script

[mrdoob]

Description

Show a message when the browser doesn't support Import Maps instead of failing silently.

[marcofugaro]

Hello @mrdoob there is now a polyfill for importmaps, what do you think about using it to start the migration to importmaps for other examples as well? 🙂

We are using it on this cannon-es-debugger example to make it run on firefox and safari as well.

This is the usage:

https://github.com/pmndrs/cannon-es-debugger/blob/4525caef5c7066e72e131ce512eff56317f59aea/index.html#L35-L48

<!-- Import maps polyfill -->
<!-- Remove this when import maps will be widely supported -->
<script async src="https://unpkg.com/es-module-shims@1.3.6/dist/es-module-shims.js"></script>

<script type="importmap">
  {
    "imports": {
      "cannon-es": "https://unpkg.com/cannon-es@0.18.0/dist/cannon-es.js",
      "cannon-es-debugger": "./dist/cannon-es-debugger.js",
      "three": "https://unpkg.com/three@0.136.0/build/three.module.js",
      "three/examples/jsm/controls/OrbitControls": "https://unpkg.com/three@0.136.0/examples/jsm/controls/OrbitControls.js"
    }
  }
</script>

[mrdoob]

Oh, that shim no longer requires doing <script type="importmap-shim">?

[marcofugaro]

Yess, it works with native syntax now.

The tradeoff is that the error in the console is still there, because the polyfill can't disable native module loading. But the example works nonetheless.

More info in its readme.

[mrdoob]

Yess, it works with native syntax now.

Interesting development... 🤩
I'll put it in the WebGPU examples for now.

/fyi @sunag